EA031035B1 - Induction motor - Google Patents

Abstract

An induction motor (1) comprises a housing (10), a stator (20), a rotor (30) and cooling fins (40) on the outside surface (10a) of the housing (10). The rotor (30) comprises inner air ducts (36) configured to allow passage of an airflow therethrough. The induction motor (1) comprises outer air ducts (50) in fluid communication with the inner air ducts (36) to form an air circulation circuit. The outer air ducts (50) are arranged radially outside the cooling fins (40).

Description

The invention relates to cooling systems for asynchronous motors.

Prior art

An asynchronous motor contains a stator, which creates a rotating magnetic field inside the cavity, and a rotor, which is mounted for rotation inside the cavity of the stator and rotates through interaction with the magnetic field created by the stator.

The stator contains a stator package, limiting the cavity, and a stator winding, which is wound on the inner peripheral part of the stator package. When current flows through the stator winding, a magnetic field is created inside the cavity.

The rotor contains a rotor package and a rotor shaft cage. The rotor cage is formed by a pair of locking rings and a set of conductive rods located between a pair of locking rings.

When the rotor is rotatably located inside the stator cavity and a current flows through the stator winding, the magnetic field created by the stator winding is applied to the rotor. This, in turn, generates a current in the conductive rods, and an electromagnetic force is generated in the rotor as a result of the interaction of the current generated in the conductive rods and the magnetic field generated by the stator. The rotor rotates due to the electromagnetic force generated by the rotor.

In the magnetic and electric circuits of the electric motor (stator and rotor packages, stator winding and rotor cage) there are power losses due to the conversion of electromagnetic energy. These losses generate heat, which must be removed to maintain the temperature of the components, compatible with the characteristics of the thermal class of materials and the required level of safe operation of the electric motor.

To remove the generated heat, the electric motor is equipped with a circulating air cooling system.

In the prior art, it is known that the fins are provided on the outer surface of the motor housing, and a fan assembly is installed on the non-driven side of the electric motor to create and direct the air flow to the fins.

For example, asynchronous motors with cooling systems are described in patent documents US 2014/0062227, US 2014/0021812 and US 2011/0068644.

Since the corresponding loss is due to the heat generated by the electric motor, the applicant considers that the cooling fins practically provide for the removal of heat generated in the rotor and that the performance of the electric motor can be improved by improving the cooling of the rotor.

Therefore, there is a need to create an asynchronous electric motor with a cooling system that enhances the cooling of the rotor.

DISCLOSURE OF INVENTION

The invention relates to an asynchronous motor, comprising a housing having an outer surface; a stator held inside said housing having a stator cavity extending in the longitudinal direction; a rotor mounted for rotation within said cavity of said stator and configured for rotation relative to said stator about an axis passing in said longitudinal direction; a plurality of circumferentially distributed cooling ribs located on said outer surface of the housing, with each cooling rib extending in said longitudinal direction and protruding outward from said outer surface between the base located on said outer surface and the free edge spaced to the edge, however, the specified distance to the edge is measured as the radial distance between the specified axis and the specified free edge, and the specified rotor contains sets o internal air channels, with each internal air channel being adapted to allow an air flow through it; said asynchronous motor comprises a plurality of external air channels communicating in fluid with said multiple internal air channels to form an air circulation circuit; each outer air channel is located adjacent to the respective one or more cooling fins, spaced and separated from said corresponding one or more cooling fins; each outer air channel extends in said longitudinal direction parallel to the respective one or more cooling ribs between the first end and the second end; each outer air channel is located outside said adjacent one or more cooling fins and is located at the minimum distance to the channel, measured as the minimum radial distance between the specified axis and the specified external air channel, and the specified minimum distance to the channel is greater than the maximum distance to the edge corresponding adjacent one or more cooling fins.

Preferably, each outer air channel is located radially outside the free edge of the corresponding adjacent cooling edge and runs parallel to the specified adjacent cooling edge, and the specified minimum distance to the channel is greater than the distance to the edge

- 1 031035 specified adjacent cooling ribs.

Preferably, said housing comprises a plurality of first openings and a plurality of second openings formed in said outer surface, wherein a plurality of first outer connecting channels is provided for connecting the first end of each outer air passage with a corresponding first opening and for connecting the second end of each outer air passage and many second outer connecting channels.

Preferably, said housing extends between the drive side and the fan side; while on the specified side of the fan there is a fan cooling unit comprising an internal fan and an external fan; however, the specified internal fan is made with the possibility of creating an air flow passing through the specified set of internal air channels and the specified set of external air channels, and the specified external fan is made with the possibility of creating and directing the air flow to the specified set of cooling fins located on the outer surface of the housing, and to a specified set of outdoor air ducts.

Preferably, said internal fan comprises an air inlet for intake and an air outlet for discharging air adjacent to one of said first and second openings.

Preferably, between the plurality of internal air ducts and the internal fan, there is an internal air guide for storing and directing air exiting the internal air channels to the internal fan; Between the plurality of internal air ducts and the first holes, an internal air guide is arranged to accumulate air exiting the first holes and direct it to the indicated plurality of internal air ducts.

Preferably, outside the plurality of cooling fins and said plurality of external air channels, a casing is positioned so that the cooling fins and the external air channels are closed between the outer surface of the housing and the casing.

Preferably, said rotor is connected to a drive shaft, said plurality of internal air channels comprises one or more groups of circumferentially distributed internal air channels, with at least one group of circumferentially distributed internal air channels formed in the said rotor in a radial position next to said driving shaft.

Preferably said rotor comprises a rotor package connected to said drive shaft, and a rotor cage connected to said rotor package; moreover, the specified at least one group distributed around the circumference of the internal air channels formed in the specified rotor in a radial position near the specified drive shaft, formed in the specified package of the rotor.

Brief Description of the Drawings

The following is a detailed description of the invention with reference to the drawings, which explain some embodiments of the invention. The drawings are sketchy.

FIG. 1 is a perspective view of an induction motor according to an embodiment of the invention;

in fig. 2 shows the engine shown in FIG. 1, a sectional view;

in fig. 3 shows the engine shown in FIG. 1, front view;

in fig. 4-7 show the engine shown in FIG. 1, other sectional views.

Embodiments of the invention

FIG. 1 shows an asynchronous motor 1.

In accordance with a preferred embodiment of the invention, the asynchronous motor 1 is a closed-type asynchronous motor with fan cooling.

The asynchronous motor 1 comprises a housing 10 and a stator 20 mounted inside the housing 10. The housing 10 has an outer surface 10a and an inner surface 10b.

Preferably, the housing 10 comprises a plurality of supporting elements 15, in this example in the form of paws for supporting the base.

The stator 20 has a stator cavity 21 extending in the longitudinal direction X-X, in which the axis A of the asynchronous motor 1 passes.

The stator 20 includes a stator packet 22 extending in the longitudinal direction X-X from the first end 22a to the second end 22b, and a stator winding 23 connected to the stator packet 22 and extending in the longitudinal direction X-X from the first end 23a to the second end 23b. The stator winding 23 projects longitudinally from the first and second ends 22a, 22b of the stator packet 22. In particular, the first end 23a and the second end 23b of the stator winding 23 protrude from the first and second ends 22a, 22b of the stator packet 22.

The rotor 30 is installed with the possibility of rotation inside the stator 20, in particular inside the cavity 21 of the stator, and is made with the possibility of rotation relative to the stator 20 around the axis A. The rotor 30 contains

- 2 031035 live drive shaft 31, passing along the longitudinal axis X-X between the first end 31a and the second end 31b. The first end 31a defines the drive connection of the asynchronous motor 1.

According to an embodiment, the rotor 30 comprises a rotor pack 32 connected to a drive shaft 31, and a rotor cage 33 connected to the rotor pack 32. The rotor cage 33 contains a plurality of circumferentially distributed rods 34 and two opposite rings 35a, 35b connected to a plurality of rods 34 distributed around the circumference. The rods 34 and rings 35a, 35b are made of electrically conductive material.

The housing 10 extends longitudinally between the first end 10c and the second end 10d. The first end 10c defines the drive side 11, and the second end 10d defines the fan side 12.

On the side 11 of the drive is located bearing unit 2 drive. The bearing unit 2 of the drive is supported by the first screen 13, which is attached to the housing 10 and is held by this housing. The bearing unit 2 of the drive side is connected to the first end 31a of the drive shaft 31 to maintain rotation and a drive function of the drive shaft 31.

On the fan side 12, a fan cooling unit 3 and a non-drive bearing unit 4 are arranged. The non-drive end bearing assembly 4 is supported by a second shield 14, which is attached to the housing 10 and held by this housing. The non-drive end bearing assembly 4 is connected to the second end 31b of the drive shaft 31 and cooperates with the drive-side bearing assembly 2 to maintain the rotation of the drive shaft 31.

The fan cooling unit 3 comprises an internal fan 5 and an external fan 6.

The internal fan 5 is located inside the housing 10 between the rotor 30 and the second screen 14 and is configured to create an air flow for cooling the rotor 30 and preferably part of the stator 20. In particular, the internal fan 20 includes an air inlet 5a and an air outlet 5b for air release.

The outer fan 6 is located outside the housing 10 behind the second screen 14 and is configured to create an air flow on the outer surface 10a of the housing 10. In particular, the outer fan 6 comprises an inlet 6a for air intake and an outlet 6b for air release.

In particular, a plurality of circumferentially distributed cooling fins 40 are located on the outer surface 10a of the housing 10. Preferably, the cooling fins 40 form a plurality of groups of cooling fins, with the cooling fins of each group parallel to each other. Each cooling rib 40 extends in the longitudinal direction X-X and protrudes outward from the outer surface 10a between the base part 43, located on the outer surface 10a, and the free edge 44 of the rib, located at a distance F1 to the rib. The distance F1 to the edge is measured as the radial distance between the axis A and the free edge 44. In other words, the distance F1 to the edge is measured along the YZ plane of the section (i.e. the plane perpendicular to the axis A and the longitudinal direction XX) as the linear distance between the axis X and a free edge 44. The distance F1 to the rib may be constant or may vary in the longitudinal direction with the first end 41 and the second end 42. In the example under consideration, each group of parallel cooling ribs extends outward in the corresponding transverse nap ION, such as Y-Y direction or in the direction Z-Z perpendicular to the longitudinal direction X-X. The transverse directions Y-Y and Z-Z lie in a plane perpendicular to the longitudinal direction X-X.

Preferably, the first end 41 and the second end 42 of the cooling fins 40 are located near the first end 10c and the second end 10d of the housing 10, respectively. Thus, the cooling fins 40 occupy essentially the entire working outer surface 10a of the housing 10.

The air flow generated by the outdoor fan 6 is directed to the cooling fins 40 to remove heat that is generated inside the housing 10, in particular the stator 20, through heat exchange with air outside the housing 10.

The internal fan 5 is connected to the second end 31b of the drive shaft 31 and is thus driven by the drive shaft 31. In particular, the internal fan 5 is mounted on the second end 31b of the drive shaft 31 and rotates together with the drive shaft 31.

According to an embodiment, the outdoor fan 6 is also connected to the second end 31b of the drive shaft 31. In particular, the external fan 6 is also mounted on the second end 31b of the drive shaft 31 and rotates together with the drive shaft 31.

In accordance with an alternative embodiment, the outdoor fan 6 may be connected to the drive shaft of the electric motor provided for this purpose. This option is predominant when the asynchronous motor 1 is a low-speed electric motor or a variable-speed electric motor. In fact, in this case, a low or adjustable rotational speed cannot provide a sufficient speed of the air flow generated by the external fan 6.

To close the outdoor fan 6 to the housing 10 is attached to the fan casing 7. The fan casing 7 has a plurality of openings 7a, allowing the external fan 6 to draw in air and create air flow directed towards the outer surface 10a of the housing 10. At the outer

- 3 031035 surfaces 10a of the housing 10, the air flow generated by the external fan 6 exchanges heat with the fins 40 to remove heat from the housing 10.

For removing heat from the rotor, the rotor 30 comprises a plurality of internal air channels 36. Preferably, the internal air channels 36 are formed in the package 32 of the rotor. Each internal air channel 36 is configured to provide an air flow through it.

In accordance with an embodiment, the internal air channels 36 form one or more groups of circumferentially distributed internal air channels. These groups of internal air channels are in different radial positions.

Preferably, the inner air channels 36 form the first group 36a of the inner air channels made in the rotor package 32. More preferably, the inner air passages 36 also form a second group 36b of the inner air passages made between two adjacent rods 34.

The first group 36a is located closer to the drive shaft 31 than the second group 36b. Each group of internal air channels contains one or more rows of circumferentially distributed internal air channels, with the rows in different radial positions.

For example, the first group 36a contains three rows of circumferentially distributed internal air channels, while the second group 36b contains one row of circumferentially distributed internal air channels.

The internal air channels of the first group 36a, which are formed in the rotor package 32, have a circular cross section. The inner air channels of the second group 36b, which are formed between two adjacent rods 34, have an elongated cross section with short and long sides, with the long sides extending in the radial direction.

For the formation of the air circulation circuit outside the housing 10, a plurality of circumferentially distributed outer air ducts 50 are provided. The outer air ducts 50 are in fluid communication with the inner air ducts 36.

The internal fan 5 is made with the possibility of creating air flow through the internal air channels 36 and external air channels 50.

In accordance with an embodiment, the internal fan 5 draws air through the internal air ducts 36 and exhausts the intake air into the external air ducts 50. Thus, the intake air accumulates some of the heat generated by the rotor 30 and then passes through the external air ducts 50 to release this accumulated heat through heat exchange with air outside the housing 10.

In accordance with an alternative embodiment, the internal fan 5 draws air through the external air ducts 50 and discharges the intake air into the internal air ducts 36. Thus, the intake air passes through the internal air ducts 36, where it accumulates some of the heat generated by the rotor 30 and then passes through the outer air channels 50 to release this accumulated heat through heat exchange with air outside the housing 10.

Each outer air channel 50 is located adjacent to the respective one or more cooling fins 40, spaced and separated from the corresponding one or more cooling fins 40.

Each outer air channel 50 extends in the longitudinal direction X-X parallel to the respective one or more cooling fins 40 between the first end 51 and the second end 52.

Each outer air channel 50 is located outside next to one or more cooling fins 40 and is at a minimum distance D1 to the channel measured as the minimum radial distance between axis A and the outside air channel 50. In other words, the minimum distance D1 to the channel is measured along the YZ plane section (i.e., a plane perpendicular to axis A and longitudinal direction XX) as the minimum linear distance between axis A and the outside air channel 50. The minimum distance D1 to the channel is greater than the maximum distance F1 to the edge of the respective one or more cooling fins 40. In other words, the outside air ducts 50 are located radially outside the plurality of cooling fins 40.

In accordance with an embodiment, the outer surface 10a of the housing 10 has a substantially cylindrical shape. A plurality of circumferentially distributed cooling fins 40 is located on the outer surface 10a of the housing 10 and protrudes outward from the outer surface 10a. In particular, a plurality of cooling fins 40 extend outward from the outer surface 10a within the annular zone surrounding the outer surface. The annular zone extends in the longitudinal direction X-X and has a substantially annular cross-section, thereby surrounding the essentially cylindrical outer surface 10a. In addition, the outer air channels 50 are located outside the annular zone, essentially in the radial direction. In addition, the outer boundary of the annular zone locally coincides with the free edge 44 of each cooling edge 40 and is located at a distance F1 from the axis A. As indicated above, the external air ducts are located outside the annular zone, i.e. at the minimum distance D1 to the channel, which exceeds the maximum distance F1 to the edge

- 4 031035 adjacent one or more cooling fins 40. For example, cooling fins 50 may contain groups of cooling fins 40, with each group of cooling fins 40 protruding from the outer surface 10a with a different orientation at a different distance F1 to the edge. As stated above, the minimum distance D1 to the channel of the external air channel 50 is locally greater than the distance F1 to the rib and may locally vary depending on the maximum distance F1 to the edge of the adjacent group of cooling fins 40. Thus, each external air channel 50 is located at a distance and is separated from the neighboring (or nearest) group of cooling fins 40.

This arrangement of the outer air channels 50 allows to separate the air flow for heat dissipation generated by the external fan 6 and directed to the cooling fins 40, mainly designed to remove the heat generated by the stator 20, and the air flow for heat dissipation generated by the internal fan 5 and passing inside the outer air channels 50, designed primarily to remove heat generated by the rotor 30.

In accordance with an embodiment, each outer air channel 50 is located radially outside the free edge 44 of the corresponding adjacent cooling edge 40. The minimum distance D1 to the channel is greater than the distance F1 to the edge of the adjacent cooling edge 40.

In accordance with an embodiment, the asynchronous motor 1 comprises a casing 16 located outside the cooling fins 40 and the outer air channels 50. Thus, the cooling fins 40 and the outer air channels 50 are closed between the casing 10 and the casing 16. The casing 16 has an outer surface 16a and an inner surface 16b. In accordance with this option, the air flow generated by the external fan 6 forcibly moves between the outer surface 10a of the housing 10 and the inner surface 16b of the housing 16. In turn, this optimizes the air flow through the cooling fins 40 and the efficiency of heat exchange with the cooling fins 40.

Preferably, a portion of the air flow generated by the internal fan 5 moves toward the second end 23b of the stator winding 23 projecting from the stator packet 23. Thus, this part of the air flow generated by the internal fan 5 accumulates heat generated by the stator winding 23 and then moves through the external air ducts 50 for heat removal.

Preferably, the first end 51 and the second end 52 of the outer air channels 50 are located near the first end 10c and the second end 10d of the housing 10.

The housing 10 comprises a plurality of first openings 17 and a plurality of second openings 18 formed in the outer surface 10a. For connecting the first end 51 of each outer air channel 50 with a corresponding first opening 17 and for connecting the second end 52 of each outer air channel 50 with a corresponding second opening 18, a plurality of first outer connecting channels 53 and a plurality of second outer connecting channels 54 are provided.

Preferably, the first openings 17 and the second openings 18 are located near the first end 10c and the second end 10d of the housing 10.

The internal fan 5 draws hot air from the rotor's internal channels 36 and directs the hot air flow to the second holes 18. Through the second holes 18, the hot air flow enters the external air channels 50 and exits through the first holes 17 at a lower temperature as a result of heat exchange carried out during movement in the outer air channels. The air flow coming out of the first holes is sucked by the internal fan 5 through the internal channels 36 of the rotor and, therefore, enters the internal channels 36 of the rotor to accumulate heat generated by the rotor 30.

Preferably, the outlet 5b of the internal fan 5 is located adjacent to the second holes 18 to reduce the attenuation of the flow between the outlet 5b of the internal fan 5 and the second holes 18.

Preferably, the internal air guide device 8 is connected to the second end 31b of the drive shaft 31 and is located between the internal air channels 36 and the internal fan 5 to accumulate air leaving the internal air channels 36 and its direction to the internal fan 5.

Preferably, the internal air guide device 9 is connected to the first end 31a of the drive shaft 31 and is located between the internal air channels 36 and the first holes 17 for accumulating air leaving the first holes 17 and its direction to the internal air channels 36.

Domestic air-guiding devices 8, 9 rotate together with the drive shaft 31.

Although the invention has been described with reference to preferred embodiments, the description is explanatory and not intended to limit the invention.

Specialists in this field can perform various modifications and implement various applications without deviating from the scope of the invention defined by the claims.

- 5 031035

Claims (9)

CLAIM 1. Asynchronous motor (1), comprising a housing (10) having an outer surface (10a); a stator (20) held within said body (10), having a stator cavity (21) extending in the longitudinal direction (X-X); a rotor (30) mounted for rotation within said cavity (21) of said stator (20) and rotatably with respect to said stator (20) about an axis (A) extending in said longitudinal direction (X-X); a plurality of circumferentially distributed cooling fins (40) located on said outer surface (10a) of the body (10), with each cooling edge (40) extending in said longitudinal direction (XX) and protruding outward from said outer surface (10a) between base (43) located on the specified outer surface (10a), and the free edge (44) located at a distance (F1) to the edge, with the specified distance (F1) to the edge is measured as the radial distance between the specified axis (A) and specified free edge (44), with it said rotor (30) comprises a plurality of internal air channels (36), wherein each internal air passage (36) is adapted to allow passage therethrough of the air flow; said asynchronous motor (1) contains a plurality of external air channels (50) that are in fluid communication with said many internal air channels (36) to form an air circulation circuit; each outer air channel (50) is located adjacent to the respective one or more cooling fins (40), is located at a distance and is separated from said corresponding one or more cooling fins (40); each outer air channel (50) passes in said longitudinal direction (XX) parallel to the corresponding one or more cooling fins (40) between the first end (51) and the second end (52), characterized in that each outer air channel (50) is located one or more cooling fins (40) located outside and is located at a minimum distance (D1) to the channel, measured as the minimum radial distance between the specified axis (A) and the specified air channel (50), with the specified minimum span standing (D1) to the channel is greater than the maximum distance (F1) to the edge of the corresponding adjacent one or more cooling fins (40). 2. Asynchronous motor (1) according to claim 1, in which each external air channel (50) is located radially outside the free edge (44) of the corresponding adjacent cooling fins (40) and runs parallel to the specified adjacent cooling fins (40), and the specified minimum the distance (D1) to the channel is greater than the distance (F1) to the edge of the specified adjacent cooling edge (40). 3. An induction motor (1) according to claim 1 or 2, wherein said housing (10) comprises a plurality of first openings (17) and a plurality of second openings (18) formed in said outer surface (10a), moreover for connecting the first end (51) each external air channel (50) with a corresponding first hole (17) and for connecting the second end (52) of each external air channel (50) with a corresponding second hole (18), a number of first external connecting channels (53) and many second external connecting channels (54). 4. Asynchronous motor (1) according to any one of claims 1 to 3, wherein said housing (10) passes between the drive side (11) and the fan side (12); while on the specified side (12) of the fan there is a fan cooling unit (3) containing an internal fan (5) and an external fan (6); however, the specified internal fan (5) is made with the possibility of creating an air flow passing through the specified set of internal air channels (36) and the specified set of external air channels (50), and the specified external fan (6) is configured to create and direct the air flow to the specified set of cooling fins (40) located on the outer surface (10a) of the body (10), and to the specified set of external air channels (50). 5. An asynchronous motor (1) according to claim 3 or 4, wherein said internal fan (5) comprises an inlet (5a) for air intake and an outlet (5b) for air outlet, located next to one of the first (17) and second holes (18). 6. Asynchronous motor (1) according to claim 5, in which between the plurality of internal air ducts (36) and the internal fan (5) there is an internal air guide (8) for accumulating and directing air coming out of the internal air ducts (36), to the internal fan (5); between the set of internal air ducts (36) and the first holes (17) there is an internal air guide device (9) for accumulating air leaving the first holes (17) and its direction to the specified set of internal air channels (36). 7. Asynchronous motor (1) according to any one of claims 1 to 6, in which outside a plurality of cooling - 6 031035 fins (40) and the specified set of external air channels (50) position the casing (16) so that the cooling fins (40) and the outside air channels (50) are closed between the outer surface (10a) of the casing (10) and the casing (sixteen). 8. Asynchronous motor (1) according to any one of claims 1 to 7, wherein said rotor (30) is connected to the drive shaft (31), said plurality of internal air channels (36) form one or more groups of circumferentially distributed internal air channels (36a), (36b), with at least one group of circumferentially distributed internal air channels (36a) formed in said rotor (30) in a radial position next to said drive shaft (31). 9. Asynchronous motor (1) of claim 8, wherein said rotor (30) contains a rotor package (32) connected to said drive shaft (31), and a rotor cage (33) connected to said rotor package (32) ; moreover, the specified at least one group of circumferentially distributed internal air channels (36a), formed in the specified rotor (30) in the radial position next to the specified drive shaft (31), is formed in the specified package (32) of the rotor. FIG. one FIG. 2 - 7 031035 FIG. 3 - 8 031035 FIG. five FIG. 6 - 9 031035 FIG. 7